AMIS-30512 Datasheet, PDF (18/30 Pages) ON Semiconductor – Micro-Stepping Motor Driver

V_COIL
div2
div4
Ssh
AMIS−30512
Sh
Csh
buf
Ch
SLA−pin
Icoil = 0
PWMsh
PWMsh
Icoil = 0
SLAT
V_COIL
SLAT
NOT (Icoil = 0)
SLA−pin
last sample
is retained
V_BEMF
t
retain last sample
previous output is kept at SLA pin
t
SLAT = 1 ≥ SLA−pin is “transparent” during
V_BEMF sampling @ Coil Current Zero
Crossing. SLA−pin is updated “real−time”.
SLAT = 0 ≥ SLA−pin is not “transparent” during V_BEMF
sampling @ Coil Current Zero Crossing. SLA−pin is
updated when leaving current−less state.
Figure 13. Timing Diagram of SLA−pin
Warning, Error Detection and Diagnostics Feedback
Thermal Warning and Shutdown
When junction temperature rises above T_TW, the thermal
warning bit <TW> is set (Table 27: SPI Status Register 0).
If junction temperature increases above thermal shutdown
level, then the circuit goes in “thermal shutdown” mode,
<TSD> bit is set and all driver transistors are disabled (high
impedance) (Table 29: SPI Status Register 2). The
conditions to reset flag <TSD> is to be at a temperature
lower than T_TW and to clear the <TSD> flag by reading it
using any SPI read command.
Over−Current Detection
The over−current detection circuit monitors the load
current in each activated output stage. If the load current
exceeds the over−current detection threshold, then the
over−current flag is set and the drivers are switched off to
reduce the power dissipation and to protect the integrated
circuit. Each driver transistor has an individual detection bit
in the Table 28: SPI Status Register 1 and Table 29: SPI
Status Register 2 (<OVCXij> and <OVCYij>). Error
condition is latched and the microcontroller needs to clean
the status bits to reactivate the drivers.
NOTE:
Successive reading the SPI Status Registers 1 and 2 in
case of a short circuit condition, may lead to damage to
the drivers.
Changing the current over different current ranges might
lead to false over current triggering.
Open Coil Detection
Open coil detection is based on the observation of 100
percent duty cycle of the PWM regulator. If in a coil 100
percent duty cycle is detected for longer than t_OC = 200 ms
then the related driver transistors are disabled
(high−impedance) and an appropriate bit in the SPI status
register is set (<OPENX> or <OPENY>). (Table 27: SPI
Status Register 0).
Charge Pump Failure
The charge pump is an important circuit that guarantees
low Rdson for all drivers, especially for low supply voltages.
If the supply voltage is too low or external components are
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